Baryta coated photographic paper



' United States Patent BARYTA COATED PHOTOGRAPHICPAPER George F. L.Wood, Rochester, N. Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey Application April 30, 1953, Serial No.352,287

2 Claims. (Cl. 96--85) This invention relates to a baryta coated papercharacterized by the presence of a layer containing barium chloride orsome other chloride to prevent the migra tion of silver salts into orthrough the paper itself from a photographic emulsion which has beenapplied thereto.

In the case of photographic papers there is often a tendency for some ofthe silver material in a photographic emulsion to migrate into andthrough the paper base which may result in discoloration of the paper oreven possibly of the emulsion itself. This has been found to beparticularly objectionable in the case of print-out emulsions, such asof the type described in U. S. Patent No. 2,126,319 of Staud andFallesen, which conventionally may contain not only silver halide butalso soluble silver. It has been noted that when printout emulsions arecoated out onto a regular baryta coated paper base the silver salts tendto migrate through the baryta layer and the paper to the back of thepaper sheet where they react with the interleaving tissue, ordinarilyused, to form objectionable discoloration of the back of thephotographic paper or often of the emulsion itself.

I have found that if the baryta coated paper contains a small proportionof barium chloride, preferably in the -baryta coating, with or withoutsodiumstearate or like salt that the discoloration of the paper andemulsion which has been noted heretofore is reduced and upon storage noobjectionable discoloration occurs. I have found it to be desirable toinclude sodium stearate or the like with the barium chloride to presentamore impermeable layer although prevention of the migration of thesilver ions into the paper is appreciably reduced merely by the presenceof barium chloride alone. I have found that a barium halide such asbarium chloride, bromide, or iodide is eminently suitable for use in thebaryta coating for inhibiting the migration of silver salts to the backof the paper sheet. Although aluminum chloride might for example beemployed for this purpose, because of its hardening tendencies towardsgelatin its field of use is more restricted than in the case of bariumchloride.

The accompanying drawing illustrates photographic paper in accordancewith my invention. This drawing shows in section the arrangement of thelayers therein in which the paper is baryta coated with a compositionwhich contains in addition to the barium sulfate and carrier therefore,barium chloride and a salt of an aliphatic acid of -20 carbon atoms overwhichis applied a silver halide photographic emulsion containing silvernitrate.

One object of my invention is to provide a baryta coated paper whichwill inhibit the migration of the silver salts from the photographicemulsion layer'to the paper base. Another object of my invention is toprovide a paper base for photographic products possessing a barrier of ametal halide to bar movement of silver from one layer to another. Afurther object of my invention is to inhibit the discoloration which hasheretofore been exhibited by some types of silver photographic emulsionson the paper support therefor. Other objects of my invention will appearherein.

In its broadest aspects my invention involves a paper support forphotographic emulsions to which a metal halide barrier has been suppliedprior to the coating of a photosensitive emulsion layer thereon. Thisbarrier should be such that there is .4-1 gram of the metal chloride persq. meter of the paper. The halide barrier to prevent the migration ofsilver salts into or through the paper base may conveniently take theform of the prescribed amount of metal halide in the baryta layerapplied to a paper base. I have found that the preferred metal halidefor use in this connection is barium chloride. I have in addition foundthat when part of this barium chloride is converted to a barium soap ofan aliphatic acid (saturated or unsaturated) of 10-20 carbon atoms thatthe prevention of the silver salt migration is enhanced. Instead ofincorporating barium chloride in the baryta layer some other halidewhich forms an insoluble soap may be employed such as aluminum chloridealthough in the case of the latter material hardening properties areexerted on the gelatin when too much of that material is employed. Othermetal halides such as sodium chloride, potassium chloride, potassiumbromide or sodium iodide can be employed in the baryta layer to preventthe migration of silver salts but preferably when the fatty acid soap isnot used in the baryta layer.

If desired the halide layer may be separate from the baryta layer. Forinstance, the metal halide may be incorporated inthe stockfrom which thepaper is formed in such amount as to be present in the finished paper inthe proportion designated. Also the metal halide may be applied as alayer to the reverse side of the paper preferably employing therewith'asmall amount of a binder such as gelatin. Alternatively the metal halidecan be applied asa layer on the paper prior'to the application of thebaryta layer. In those cases where a fatty acid soap such as sodiumstearate is employed in the baryta coating layer, it is ordinarilyadvisable to employ a chloride other than that of sodium or potassium asin some cases where alkali metal chlorides are used objectionablefoaming has occurred.

As pointed out above my invention relates to the prevention' of themigration of silver salts in finished photographic paper but as thisphenomena is characteristic of the print-out types of emulsions myinvention is especially adapted to papers containing emulsions of thattype. The proportion of barium halide specified herein as being usefulfor preventing the migration of silver salts is ordinarily obtained in abaryta coating composition by the use of at least 4% of BaCla-ZHzO basedon the dry weight of the solid materials in that composition. Thisminimum would depend upon the concentration at which the baryta coatingcomposition was used and the thickness with which the baryta compositionis applied to the surface of the paper. It is desirable to use at least10 parts of barium chloride per part of sodium stearate or like salt inthe coating composition. As has been indicated above the sodium stearateor other soap may be completely omitted although it has been found/thatthe presence of a small amount of soap is desirable to further reducethe penetration of silver salt tinuouslyby passing the paper over theroll wet with i I baryta solution, contact being assured by an idling orpressing roll. In any of the baryta coating operations it would begenerally advisable toregulate thethickness of thebaryta coating bymeansof adoctor bladeyair. brush, or the like, after which the barytacoatedpaper may .be

dried and collected upon a roll in the preferred prepara- 'tion,of abaryta coated paper. A convenient method of operation is to first coatthe paper with a baryta coating "containing the metal halide with orwithout, soap and after drying that coating to apply a second barytacoating without the metal halide therein which is then followed bydrying and a calendering of the baryta coated paper.

This paper may be converted into a photographic paper 'by'applying alayer of sensitive photographic emulsion -thereon.' As my inventionisparticularly adapted to the .manufacture of photographic papers usingemulsions hav- .ing soluble silver therein in addition to silver halidethat .type of emulsion would ordinarily be employed for s ensi- "tizing'the paper.

Nevertheless it is to be understood that my invention is adapted to thepreparation of photographic paper generally and any photosensitivesilver halide emulsion but especially of the gelation-silver type 'maybe used for the photosensitive coating.

When the barrier to the migration of silver salts is to be incorporatedin the baryta layer the baryta coating composition may conveniently beprepared in the following manner:

A paste of barium sulfate in water is first prepared having aconsiderable proportion of barium sulfate therein. There is then runinto the barium sulfate paste an aqueous solution of barium chloridefollowed by the addition of a mixture of a gelatin solution and asolution of an alkali metal soap such as sodium stearate with.thoroughmixing; this mixing preferably taking place at an elevatedtemperature. After these materials have been The mass is preferably runpliedto the paper.

This method of preparing the baryta coating has been found to be usefulwith various concentrations of barium chloride and sodium stearate. Forinstance, the barium chloride ordinarily should constitute at least 4%of the total dry ingredients of the baryta but proportions above thisamount may be employed in the method described.

In some cases proportions of sodium s'tearate'or barium chloride or bothmay be employed in which then there may be some tendency towardscoagulation in preparing the baryta composition'and hence care must beexercised. However; where the proportions are such that there is .nodanger of coagulation occurring the baryta coating composition may beprepared by combining the constituents thereof in most any desired orderparticularly as regards the sodium stearate (or like soap) andthe'barium chloride as is illustrated by the order in which thematerials are combined in the examples given. When so- ,dium stearate orsome other soap is employed it is desired that the metal halide such asbarium chloride be employed in the proportion of -20 parts per part ofsoap.

Although sodium stearate being the more common type of soap wouldordinarily be employed Where soap is indicated nevertheless any of thealkali metal salts of the aliphatic acids of 10-20 carbon atoms aresuitable for use in this connection such as sodium palmitate, sodiummyristate, sodium oleate, sodium laurate, sodium palmitoleate or thelike. 7

The following examples illustrate my invention:

Example I A baryta coating composition was prepared by soaking anddissolving 36 lbs; of gelatinin 180 lbs-of water at 180 F. After thegelatin has been dissolved there was added thereto 86.5 lbs. of a 3%aqueous solution of sodium stearate while hot and the mass was wellmixed. The above mixture was then introduced into a 630 lb. water pasteof barium sulfate having a 45% solid content. The mass was well stirredand heated to 150 F. 13.8 lbs. of Bal2-2H2Owas dissolved in 75 lbs. ofwater and was added to the barium sulfate paste and mixed for tominutes. There was then added 18 lbs. of butyl alcohol and the mass wasrun through a homogenizer to second baryta coating but of theconventional kind was applied to the paper, the coating was dried andthe paper period oftimeL was calendered by passing through heated rolls.

The

paper was then collectedv in the form of rolls.

Photographic print out paper wasprepared from the paper so formed byapplyingthereto in the conventional manner a silver halide gelatinphotographic emulsion containing a substantial proportion of unreactedsilver nitrate therein. This paper was packaged by insertinginterleaving papersheets .between sheets of the photol graphic paper; Itwas found that there was no formation of spots orstains in either theemulsion layer or in the paper itself, after storage of the paper for aconsiderable Example:

. A paper was prepared as described in the preceding example bydissolving 36 lbs. of gelatin in 180 lbs. of water and adding thereto157 lbs.of a 3% aqueous sodium -stearate solution in the describedmanner. was then poured into 945 lbs. of an aqueous paste con- T hismixture sisting of 55% of water and 45% of barium sulfate which mixturewas heated to F. and well stirred. 25 lbs. of BaClz-ZI-IgO was-dissolvedin 200 lbs; of water. This .solution was added to the barium sulfatemass and mixing was continued for 1-5 to 20 minutes. There was thenadded to the mass. 58 lbs. of a formaldehyde hardener with continuedmixing and then '23 lbs. of butyl alcohol. .The mass .was then improvedby subjecting to a homogenization. The mass thus formed was thinned withwater -to the desired consistency and applied as a coating to paper inthe conventional manner.

The thus formed paper was coated with a print-out type of silver halidegelatin emulsion containing asubstantial proportion of silvernitratethe'rein. The so formedpaper was dried and packagedusinginterleaving sheets to separate the sheets of photographic paper.After storage for a considerable period of time the paper was found tobe free of discoloration andaspotting' whereas paper of like typeprepared without the use ofb'arium chloride and sodium stearate in thebaryta coating showed a high degree of discoloration both in the paperand in the emulsion layer. i I

I claim:

1.: A'photographic print-out paper comprising a paper base, a barytacoating thereon resulting from applying 'to the paper a'composition ofbarium sulfate, a binder, a salt of an aliphatic acid of 10-20 carbonatoms and barium chloride, the latter. in an amount of'.4-1 gram persquare meter of surface and a gelatin silver halide photographicemulsion layer containing a substantial proportion of silver nitratetherein. 0

. 2. A photographic print-out paper comprising a paper .base, a barytacoating thereon resulting from applying to'the paper a composition madefrom barium sulfate, a binder, sodium stearate and 'barium'chlo'ride,which layer was applied to provide .4-1 gram of barium chloride per 5square meter of surface and a gelatin-silver halide photo- 916,616graphic emulsion layer containing a substantial propor- 1,386,995 tionof silver nitrate therein. 1,504,150 2,366,723 References Cited in thefile of this patent 5 UNITED STATES PATENTS 21884 804,039 Pifer Nov. 7,1905 6 Schwartz Mar. 30, 1909 Dorel Aug. 9, 1921 Schloemann Aug. 5, 1924Galley Jan. 9, 1945 FOREIGN PATENTS Great Britain of 1914

1. A PHOTOGRAPHIC PRINT-OUT PAPER COMPRISING A PAPER BASE, A BARYTACOATING THEREON RESULTING FROM SUPPLYING TO THE PAPER A COMPOSITION OFBARIUM SULFATE, A BINDER, A SALT OF AN ALIPHATIC ACID OF 10-20 CARBONATOMS AND BARIUM CHLORIDE, THE LATTER IN AN AMOUNT OF .4-1 GRAM PERSQUARE METER OF SURFACE AND A GELATIN SILVER HALIDE PHOTOGRAPHICEMULSION LAYER CONTAINING A SUBSTANTIAL PROPORTION OF SILVER NITRATETHEREIN.